1、UDP下载

#include<myhead.h>#define ERR_MSG(msg)  do{\fprintf(stderr, "__%d__:", __LINE__); \perror(msg);\
}while(0)#define SER_PORT 8888               //端口号，范围1024~49151
#define SET_IP  "192.168.114.85"   //本机IP，ifconfigint do_download(int cfd,struct sockaddr_in sin);int main(int argc, const char *argv[])
{//创建报式套接字 socketint cfd = socket(AF_SOCK_DGRAM,0);if(cfd < 0){ERR_MSG("socket");return -1;}printf("socket create success cfd=%d\n",cfd);//填充服务器的地址信息结构体，给sendto函数使用struct sockaddr_in sin;sin.sin_family    = AF_INET;sin.sin_port      =htons(SER_PORT);sin.sin_addr.s_addr=inet_addr(SER_IP);char choose = 0;while(1){system("clear");printf("--------------------------\n");printf("------------1.下载--------\n");printf("------------2.上传--------\n");printf("------------3.退出--------\n");printf("--------------------------\n");printf("请输入>>>");scanf("%c",&choose);while(getchar() !=10);//循环吸收垃圾字符，直到吸收到\n字符switch(choose){case '1':do_download(cfd,sin);break;case '2':break;case '3':goto END;break;default:printf("输入错误，请重新输入\n");break;}printf("输入任意字符清屏");while(getchar()!=10);}
END://关闭套接字close(cfd);return 0;
}int do_download(int cfd,struct sockaddr_in sin)
{char buf[516] = "";char filename[20] = "";printf("请输入要下载的文件名>>>");scanf("%s",filename);while(getchar()!=10)unsigned short* ptr1 = (unsigned short*)buf;*ptr1 = htons(1);char* ptr2 = buf+2;strcpy(ptr2,filename);char* ptr4 = ptr2+strlen(filename)+1;strcpy(ptr4,"octet");int size = 2+strlen(ptr2)+1+strlen(ptr4)+1;if(sendto(cfd,buf,size,0,(struct sockaddr*)&sin,sizeof(sin)) < 0){ERR_MSG("sendto");return -1;}printf("sendto download request success\n");while(1){//接收数据 recvfrom,接收地址信息//组ACK包//发送ACK sendto//判断数据是否小于512个字节，若小于则下载完成}return 0;
}

2、思维导图